Other Possibilities for the Cause of the Extinctions at the K/T Boundary:

Reversal of the Earth's Magnetic Field

Periodically in Earth's history the magnetic field switches; in effect North becomes South and South becomes North. This causes the magnetosphere to weaken, allowing the Earth's ionizing radiation to enter the atmosphere and reduce the ozone layer. Life on the surface would be bombarded by heavy amounts of UV radiation.

Natural Climate Change

Various studies such as oxygen isotope analysis of planktonic and benthic foraminifera (Douglas and Savin 1973), angiosperm leaf physiognomy (Wolfe and Upchurch, 1987) and change in the pollen record (Fredericksen, 1989), concluded that a time of long term climate change was in progress at the K/T boundary (Hallam and Wignall, 1997).

Marine Regression

An analysis of the epicontinental marine sections of the K/T boundary concluded that the sea level at the time dropped, followed by a rise (Hallam, 1992).

Back to Volcanism	Back to Main Page	Go To Causes of Dinosaur Extinction